Percussion fuse

ABSTRACT

The percussion fuse is intended to be mounted on a spinstabilized projectile. The fuse includes a movable rotor subjected to the action of a retractable blocking member adapted to retain the rotor in its safety position, this blocking member being necessarily maintained in an active position by a centrifugal locking device of the percussion element of the fuse as long as this locking device remains operative; the release of this locking device permits the retraction of the blocking member under the action of return means, which retraction then permits the rotor to pass from its safety position to its armed position under the action of the centrifugal forces caused by the spin of the projectile.

United States Patent Inventor Look Blrflgt Pliny-Geneva, Switzerland Appl. No. 735,399 Filed June 7, 1968 Patented June 22, 1971 Assignee Brevets Aero-Mecanlques S. A.

Geneva, Switzerland Priority June 9, 1967 Luxembourg 53,848

PERCUSSION FUSE 5 Claims, 6 Drawing Figs.

US. Cl 102/79, 102/78, 102/80 1m. Cl I F42c 15/34, F42c 15/ 429 71 Field of Search 102/79, 78 80 References Cited UNITED STATES PATENTS 2,707,918 5/1955 Clay 102/79 Primary ExaminerSamuel Feinberg Assistant Examiner-Thomas B. Webb Attorney-Larson, Taylor & Hinds ABSTRACT: The percussion fuse is intended to be mounted on a spin-stabilized projectile. The fuse includes a movable rotor subjected to the action of a retractable blocking member adapted to retain the rotor in its safety position, this blocking member being necessarily maintained in an active position by a centrifugal locking device of the percussion element of the fuse as long as this locking device remains operative; the release of this locking device permits the retraction of the blocking member under the action of return means, which retraction then permits the rotor to pass from its safety position to its armed-position under the action of the centrifugal forces caused by the spin of the projectile.

PATENTEDJUNZZIBTI 3,585,935

' SHEET 1 OF 2 PATENTEU JUH22 I97! 3585935 sum 2 or 2 PERCUSSION FUSE The present invention relates to rotor type percussion fuses for spin-stabilized projectiles. This expression designates here, among the percussion fuses intended to equip projectiles driven after the shot fired with a spin about their axis, those comprising a percussion element maintained inoperative before the shot is fired by a first locking device releasable by the action of the centrifugal forces brought into play by the spin of the projectile. This first locking device is designated hereafter as centrifugal locking device of the percussion element." Said percussion fuses have also an explosive member (generally a detonator) adapted to assure the firing of the charge of the projectile, and furthermore, a rotor mounted rotatably in the body of the fuse about an axis perpendicular to the axis of the fuse. This rotor, which contains an explosive charge adapted to play the role of a relay with respect to the above-mentioned explosive member, is arranged in a manner to pass, under the eflect of the centrifugal forces brought into play by the spin of the projectile, from an inactive position (called "safety position") in which the explosive charge playing the role of a relay is out of alignment with the percussion element and with the explosive member, to an active position (called armed position) in which the percussion element, the relay charge and the explosive member are aligned. The invention is more particularly, but not exclusively, concerned with fuses of this type which include a self-destruction system and in which the centrifugal locking device of the percussion element comprises a spiral strip whose time of unwinding, under the effect of the centrifugal forces, conditions the release of the percussion element. It thus confers a muzzle safety" on the projectile, that is to say guarantees that this projectile cannot be fired by the fuse before having travelled a certain distance beyond the muzzle of the gun. Such spiral strip-type fuses of this type being particularly suitable for projectiles of small caliber (for example from 20 to 50 millimeters.)

The chief object of the invention is to provide a fuse of the type in question, which fulfill the requirements of practice, and in particular, which avoids the risk of premature firing in case of violent impact (with crushing of the nose of the fuse) preceding the release of the percussion element.

According to the principal feature of this invention, the movable rotor of the fuses of the type in question is subjected to the action of a retractable blocking member adapted to retain the rotor in its safety position, this blocking member being necessarily maintained in an active position by the centrifugal locking device of the percussion element of the fuse as long as this locking device remains operative, the release of this locking device having the effect of permitting the retraction of the blocking member under the action of appropriate return means, which retraction then permits the rotor to pass from its safety position to its armed position under the action of the centrifugal forces brought into play by the spin of the projectile.

Other features and advantages of this invention will become apparent from the following specific description, of several embodiments of percussion fuses according to the invention given merely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 represents, in axial section of a first embodiment, a percussion fuse established according to the invention;

FIG. 2 is a longitudinal section along lI-II of FIG. 1;

FIG. 2bis represents, in the same conditions as FIG. 2, a variant of the first embodiment;

FIG. 3 represents, in elevation with parts removed, a second embodiment of a percussion fuse according to the invention; and

FIGS. 4 and 5 represent, in the same conditions as FIG. 3, two other embodiments of a fuse according to the invention.

The fuses shown in the drawings are point detonating percussion fuses including a movable rotor and a spiral strip type muzzle safety system, for spin-stabilized projectiles of small caliber (from to 50 millimeters).

The fuse comprises, as shown in FIG. I, a fuse body 1 serving as a support for the following elements and devices:

A percussion element such as for example an axial firing pin 2 is provided with a self-destruction system and carries at its frontend a collar 3 provided in its periphery with a ring of balls 4 bearing against a trunconical shoulder 5 directed towards the front so that, under the effect of the centrifugal acceleration, these balls 4, by bearing against the frustoconical shoulder 5, tend to drive the assembly of the firing pin 2 (including its collar 3 and the balls 4) towards the front. This occurs against the action of a return spring 6, until this firing pin assembly bears against the bottom 7 of a housing 8 adapted to receive it, this bottom 7 transmitting the percussion shock during the impact, whereas in the absence of percussion shock and once the spin has slowed down sufficiently, the spring 6 will become predominant and will drive the firing pin assembly towards the rear, and thus cause the percussion of the fuse.

A detonator or the like device 9 is fixed, for example by screwing, to a plug 10 fitted at the rear of the fuse body 1, for example also by screwing.

A rotor element 11 is mounted rotatably, between the firing pin 2 and the detonator 9, about an axis perpendicular to the axis of the fuse, this rotor, in which is formed a diametrical well 11a containing a relay charge 12, being capable of passing by rotation, under the effect of centrifugal force, from the safety position illustrated in FIG. 1 to an armed position (not shown). In this armed position the well 11d (hence the relay charge 12) is located in line with the firing pin 2 and the detonator 9 which is fired in case of impact from the relay charge 12 after the destruction of a thin safety wall 13 separating the detonator from the relay charge.

A spiral strip type centrifugal locking device is arranged in a manner to release the firing pin 2 only after a certain distance of flight of the projectile corresponding to the desired muzzle safety. This locking device can advantageously comprise, as illustrated in FIGS. 1, 2 and 2bis, an expansible annular bolt 14 split along a generatrix and surrounded towards the rear (FIGS. 1 and 2) or towards the front (FIG. 2bis) by a spiral strip 15. The assembly is maintained by a split ring 16 adapted to open out radially under the effect of centrifugal acceleration, then to permit progressive unwinding of the spiral strip 15 until the release of the bolt 14 which can then open out radially releasing in its turn the firing pin 2.

It appears appropriate, at this point of the description and before considering the principal feature of the invention, to indicate briefly how a percussion fuse, constructed as has just been described, would behave, without special and supplementary precautions.

When the shot is fired and under the effect of the centrifugal force brought into play by the spin of the projectile, on the one hand, the rotor 11 would right itself immediately, and on the other hand, after expansion of the split ring 16, the spiral strip 15 would unwind progressively to permit finally the expension of the bolt 14 and the release of the firing pin 2 after a lapse of time characterizing the muzzle safety provided by the fuse of the projectile.

It will be appreciated, in these conditions, that in case of accidental impact during this lapse of time against a hard object, there is a risk, even though the firing pin 2 has not yet been released, of the untimely firing of the detonator 9 (and consequently of the projectile) by crushing of the nose of the fuse and excitation of the relay charge 12 which would already be aligned with the firing pin 2 and the detonator 9, such a risk compromising in fact the muzzle safety of the projectile.

The object of the principal feature of the present invention is precisely to mitigate this disadvantage, that is to say to reduce the risk of such a premature and untimely firing of the detonator 9.

According to this principal feature, the movable rotor 11 is subjected to the action of a retractable blocking member 17 adapted to retain this rotor in the safety position illustrated in FIG. 1, this blocking member 17 being necessarily maintained in active position by the centrifugal bolt 14 as long as this bolt is located in its locking position. The expansion of the bolt in question, at the end of the muzzle safety time hasthe effect of permitting the retraction of this blocking member 17 under the effect of appropriate return means.

In this manner, it is made quite certain that the rotor l 1 can only rotate to come into its armed position once the muzzle safety time has expires, which excludes any risk of premature and untimely firing of the detonator 9.

with regard to the return means for the blocking member 17, they can be realized, either, by mechanical means such as for example springs (not shown) or ramps carried by a movable part of the fuse urged by accelerations (centrifugal or axial) to which the projectile is subjected, or, by arrangements of the blocking member 17 in a manner such that, once released by the bolt 14, it retracts automatically under the effect of accelerations (centrifugal or axial) to which the projectile is subjected, or again, by the conjugated action of such mechanical means and arrangements.

Although there are many ways of forming the blocking member 17, taking into account what has just been described, it seems more particularly advantageous to use, for this purpose, one of the following embodiments.

According to a first embodiment, illustrated in FIGS. 1, 2 and 2bis, the blocking member 17 comprises a capsule coaxial with the firing pin 2 and having a lateral cylindrical wall and a convex curved bottom 17a fitting into a socket A of complementary form formed in the zone of the rotor ll located adjacent to the firing pin when this rotor is in its safety position. The capsule-type block member 17 is guided axially in a bore formed in the center of a transverse partition 18 serving as a support for the bolt 14 and the outer diameter of this capsule being such that the front edge of its lateral wall abuts against the rear edge of the bolt 14 when this bolt is in its locking position (case of FIGS. 1, 2 and Zbis).

In the case of this embodiment, the socket A is not very deep and the curved bottom 17a of the capsule-type block member 17 assumes the form of a portion of a sphere, which permits the rotor 11 to exert, during its rotation, a ramp effect (on the side of the socket A) to cause the retraction of this capsule by an axial movement directed towards the front.

The operation of such a fuse is then the following: from the firing of the shot, the balls 4 cause the advance of the firing pin 2 and of the collar 3 which comes to bear against the bottom 7 of the housing 8; since the split ring 16 is circumferentially expandible, the spiral strip unwinds progressively, after which the centrifugal bolt opens, permitting the retraction of the capsule 17, then the rotation of the rotor 11 which only then comes to occupy its armed position.

According to a second embodiment illustrated in FIG. 3, the lateral wall of the capsule-type block member 17 remains cylindrical but the bottom 17a of this capsule and the socket A are given a frustoconical form and a greater height, the other elements of the fuse remaining unchanged.

According to a third embodiment, illustrated in FIG. 4, the outer lateral wall of the capsule 18 is given a trunconical form with the large base directed towards the front, the bottom 17a of this capsule and a socket A having the same spherical curved form as in the case of FIG. 1.

Finally, according to a fourth embodiment, illustrated in FIG. 5, the rotor blocking member comprises, instead of a capsule, a longitudinal pin 17 bearing towards the front against the bolt 14 and engaged towards the rear in a notch E formed in the rotor 11.

Whatever embodiment is adopted, a muzzle l-l safe percussion fuse is obtained whose safety advantages are brought out sufficiently clearly from the preceding description that it is not necessary to give any further explanation in this connectron.

Needless to say, various changes and modifications are possible without departing from the spirit or scope of the present invention, so that the invention should not be limited to the particular embodiments described merely by way of example.

What I claim is: l. A percussion fuse adapted to be mounted on a sprn-stabil' ized projectile to spin therewith, said percussion fuse comprising:

percussion element,

a locking device adapted to cooperate with said percussion element, said locking device having a lock position in which it locks said percussion element, and a release position in which it releases said percussion element, said locking device being adapted to be moved from its lock position to its release position by the action of the centn'fugal force caused by the spin, thus releasing said percussion element only after a time delay,

a detonator,

a rotor mounted between said percussion element and said detonator, said rotor having a safety position and an arm position, and being adapted to be moved, when it is released, from its safety position to its armed position by the action of the centrifugal force caused by the spin,

and a retractable blocking member adapted to cooperate with said rotor, said blocking member having a block position in which it blocks said rotor in its safety position, and a release position in which it releases said rotor, said blocking member being adapted to retract to its release position, when it is released by said locking device, to release said rotor.

2. A percussion fuse according to claim 1, wherein retraction means are provided provided, adapted to cooperate with said retractable blocking member for retracting said blocking member.

3. A percussion fuse according to claim 1, wherein said. retractable blocking member is adapted to retract under the action of forces of acceleration to which the fuse is subjected.

4. A percussion fuse according to claim 1, wherein said blocking member comprises a capsule coaxial with said percussion element, said capsule fitting, in the block position of said blocking member, into a socket of corresponding shape formed in the zone of said rotor located adjacent to said percussion element when said rotor is in its safety position, said capsule being guided axially in a bore formed in a transverse wall of the fuse.

5. A percussion fuse according to claim 1, wherein said blocking member comprises a longitudinal pin which, when said blocking member is in its block position, bears towards the front against said locking device, and engages towards the rear in a notch formed in said rotor. 

1. A percussion fuse adapted to be mounted on a spin-stabilized projectile to spin therewith, said percussion fuse comprising: percussion element, a locking device adapted to cooperate with said percussion element, said locking device having a lock position in which it locks said percussion element, and a release position in which it releases said percussion element, said locking device being adapted to be moved from its lock position to its release position by the action of the centrifugal force caused by the spin, thus releasing said percussion element only after a time delay, a detonator, a rotor mounted between said percussion element and said detonator, said rotor having a safety position and an arm position, and being adapted to be moved, when it is released, from its safety position to its armed position by the action of the centrifugal force caused by the spin, and a retractable blocking member adapted to cooperate with said rotor, said blocking member having a block position in which it blocks said rotor in its safety position, and a release position in which it releases said rotor, said blocking member being adapted to retract to its release position, when it is released by said locking device, to release said rotor.
 2. A percussion fuse according to claim 1, wherein retraction means are provided provided, adapted to cooperate with said retractable blocking member for retracting said blocking member.
 3. A percussion fuse according to claim 1, wherein said retractable blocking member is adapted to retract under the action of forces of acceleration to which the fuse is subjected.
 4. A percussion fuse according to claim 1, wherein said blocking member comprises a capsule coaxial with said percussion element, said capsule fitting, in the block position of said blocking member, into a socket of corresponding shape formed in tHe zone of said rotor located adjacent to said percussion element when said rotor is in its safety position, said capsule being guided axially in a bore formed in a transverse wall of the fuse.
 5. A percussion fuse according to claim 1, wherein said blocking member comprises a longitudinal pin which, when said blocking member is in its block position, bears towards the front against said locking device, and engages towards the rear in a notch formed in said rotor. 